Using crushed rock products as a soil amendment or for enhanced plant growth is an old method and literature on this topic goes back to the early 20^th century and before. However, the systematic conceptualization of terrestrial mineral reactions as a carbon capture strategy was prominently outlined in an article by Schuiling and Krijgsman (2006). Their work might be seen as a pivotal starting point for systematically discussing the method of Enhanced Weathering in the scientific literature, which was now 20 years ago. Early studies evaluated underlying principles and tried to assess the carbon dioxide removal (CDR) potential. As the research field of Enhanced Weathering became more mature, additional aspects and processes were brought into the discussion. Considering the nearly unlimited possible combinations of the application of ground rock/alkaline products to the terrestrial system – across different soil systems, located in different climates and including diverse ecosystems or agricultural systems - makes the understanding of the underlying processes and rates of matter transfer highly relevant. This includes, liberating cations from rock/alkaline material, “parking” cations in soil pools, assessing the influence of organic acids, carbonate formation, changes in soil organic carbon, transport of alkalinity or co-benefits with other CDR-methods. I will reflect on this journey, which began in the specialized domain of geology and geochemistry and has since evolved into a highly interdisciplinary research field at the intersection of agronomy, climate policy, and economics. While many aspects remain to be fully elucidated, an Enhanced Weathering CDR industry is emerging, with carbon credits already issued. Therefore, ongoing, collaborative research remains critical to refining our understanding of geochemical uncertainties and environmental co-benefits.

How to cite: Hartmann, J.:  About 20 years of science on terrestrial Enhanced Weathering , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8365, https://doi.org/10.5194/egusphere-egu26-8365, 2026.

Enhanced weathering (EW) is a promising, scalable approach to carbon dioxide removal (CDR). It involves accelerating the weathering of minerals in soils to convert atmospheric CO₂ into carbonate alkalinity. Despite numerous studies, it remains unclear which soil/feedstock combinations achieve the highest alkalinity export and greatest CDR. This uncertainty remains because results strongly depend on experimental design, environmental conditions and soil/feedstock types.

We systematically investigated alkalinity formation and the fate of released or retained cations in a large-scale greenhouse experiment. Over a period of two years, we operated 10 L lysimeter mesocosms that grew English ryegrass (Lolium perenne) under controlled accelerated weathering conditions (>19 °C and > 2,000 mm irrigation per year). We tested four soil types with thirteen feedstocks and recorded alkalinity and cation export in soil water leachates monthly. For a subset of the samples, we quantified soil cation pools using sequential extractions (exchangeable, carbonate-bound, oxides and clay/silicate fractions) to determine the potential temporary reservoirs and irreversible cation sinks.

Our results show that the amount of weathering products entering the leachate varied substantially: although several treatments showed increased cumulative leachate alkalinity relative to their controls, some soil/feedstock combinations showed no change or even reduced alkalinity export, including for the same feedstock applied to different soils. Alkalinity production generally followed expected dissolution kinetics (steel slag > limestone/carbonate-rich metabasalt > peridotite > basanite). Highest leachate alkalinity export relative to control was observed in acidic soils, whereas little to no relative change observed in more neutral ~pH 7 soils could reflect suppression of mineral dissolution and carbonate saturation and precipitation. Soil cation pool distribution shifted markedly within the first year, and collectively retained 10 to 50 times more cations than exported as alkalinity. This implies that short-term 'realised' CDR as exported carbonate alkalinity can be far lower than the potential unrealised CDR that could be unlocked when cations are released from temporary soil retention pools.

A follow-up greenhouse experiment on 23 soils and 22 feedstocks was commenced in early 2025, spanning more than 300 soil/feedstock combinations. This expanded dataset will enable more robust attribution of controls on EW performance, such as soil pH/buffering capacity, mineralogy and reactive Ca–Mg supply. This setup will also allow identification of soil/feedstock combinations that maximise alkalinity generation under minimal cation retention in non-exportable pools. We will for the first time share early results from this follow-up experiment.

Our results emphasise that robust CDR quantification for EW should consider cation binding dynamics and pool transfers, as well as mineral saturation effects. Leachate-based alkalinity measurements alone provide an incomplete picture of available weathering products, particularly when rapid soil retention dominates early stage dynamics.

How to cite: Hammes, J. S., Hartmann, J., Barth, J. A. C., Linke, T., Smet, I., Hagens, M., Pogge von Strandmann, P. A. E., Reershemius, T., Casimiro, B., Vienne, A., Stoeckel, A. A., Steffens, R., Murphy, M. J., and Paessler, D.: Rock/soil interactions governing alkalinity release and cation retention in greenhouse enhanced weathering experiments, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8083, https://doi.org/10.5194/egusphere-egu26-8083, 2026.

Enhanced rock weathering (ERW) has the potential of being a comparatively cheap carbon dioxide removal method, as most infrastructure already exists. However, questions still remain on both dissolution rates of the feedstock added to agricultural fields, as well as processes that reduce the efficiency of the CO₂ drawdown reaction.

Such significant process are the soil’s cation exchange capacity (CEC) and secondary mineral formation. These take up elements from the dissolving feedstock, and retain them on timescales varying from several years (CEC) to thousands of years (secondary minerals).

In this study we have sampled 10 fields in Germany 27 months years after they were amended with Eifelgold basalt by the Carbon Drawdown Initiative. These samples, combined with pre-amendment and control samples, allow us to examine feedstock dissolution and secondary mineral formation on fields that subsequently underwent standard agricultural use. Amendment amounts vary between 12 and 48 t/ha, and the fields also have a range in cation exchange capacity and soil pH.

We use a combination of SOMBA (soil mass balance approach – i.e. cation/Ti ratios determined by isotope dilution (Suhrhoff et al., 2025)), sequential leaching of the soils to separate different secondary phases, and lithium isotope ratios. The latter are fractionated by secondary mineral formation, and provide a highly sensitive method to estimate secondary mineral neoformation (Pogge von Strandmann et al., 2025).  

Based on these methods, between 25 and 45% of the feedstock dissolved during the 27 months of reaction. Of this dissolved material, on average 40% was taken into the CEC, 15% into carbonates, 4% into oxides and <10% into clays.

Thus, between 3 and >20% of the total feedstock actually remained in solution after secondary mineral formation, with an additional 3 to 16% of the total feedstock temporarily retained by cation exchange. These values align with those predicted for German climate from weathering experiments and natural basalt samples.

Pogge von Strandmann P. A. E., He X., Zhou Y. and Wilson D. J. (2025) Comparing open versus closed system weathering experiments using lithium isotopes. Applied Geochemistry 189, 106458.

Suhrhoff T. J., Reershemius T., Jordan J. S., Li S., Zhang S., Milliken E., Kalderon-Asael B., Ebert Y., Nyateka R., Thompson J. T., Reinhard C. T. and Planavsky N. J. (2025) An Updated Framework and Signal-to-Noise Analysis of Soil Mass Balance Approaches for Quantifying Enhanced Weathering on Managed Lands. Environmental Science & Technology 59, 26440-26453.

How to cite: Pogge von Strandmann, P., Hammes, J., Steffens, R., Stöckel, A. A., Smet, I., and Paessler, D.: Assessing mineral dissolution and secondary mineral formation during enhanced weathering on agricultural sites, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4047, https://doi.org/10.5194/egusphere-egu26-4047, 2026.

Theobroma cacao is a cash crop that is both economically important and environmentally intensive, presenting a major sustainability challenge. In Brazil, cacao production is largely carried out by smallholder farmers on highly weathered, nutrient-poor, acidic soils (Oxisols and Ultisols). These soils have low fertility due to acidic pH, phosphorus (P), and potassium (K) levels, but high aluminium (Al) content. Enhanced rock weathering (EW) could be a pathway to access carbon financing while potentially having a ‘liming’ effect, which increases nutrient availability by raising the soil pH. However, evidence-based empirical data demonstrating the utility of EW-cacao on carbon capture and the impact of rock-dust spreading on agronomic productivity and forest ecosystem health are currently lacking.

Here we report on a field trial spanning three years that has been designed to evaluate EW deployment on cacao under field conditions. Within Brazil, specifically Bahia, cacao is often grown in a multi-strata, forest-like environment, known locally as the ‘Cabruca’ system. This system has cultural and environmental significance, often cited for its preservation of endemic trees (Cassano et al., 2008). This field trial investigates EW on both traditional and commercial agroforestry systems to determine potential synergies and additive effects. Carbon removal rates (CDR), soil fertility and agronomic co-benefits have been assessed.

Here, we present the outcome of this trial after two years of EW (basalt) application and a parallel trial assessing the potential for a novel iron chelating biotechnology to accelerate EW and CDR rates in a field setting after 9 months. We show that carbon removal can be monitored through the magnetic extraction of weathered basalt grains and their subsequent analysis. We also discuss the implications of using an iron chelator to disrupt the rock surface passivating layer for cation loss, particularly calcium. In addition, we report on important agronomic indicators, including tree height, canopy size, pest and disease incidence rate, litterfall rates and yield after two years of basalt application.

How to cite: Steeley, I., Sousa, A., França, E., Freitas, L., Martin, D., Cobbold, V., Planavsky, N., Epihov, D., and Beerling, D.: Towards Sustainable Chocolate: Two Years of Enhanced Weathering in Tropical Cacao Agri-Ecosystems, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19336, https://doi.org/10.5194/egusphere-egu26-19336, 2026.

The effectiveness of enhanced rock weathering (ERW) for carbon dioxide removal (CDR) in open systems, such as forests, remains poorly quantified. Although ERW has been deployed predominantly in agricultural systems, its performance in forestry contexts remains underexplored despite its substantial mitigation potential. Forests offer the potential for both inorganic and both above- and belowground organic CDR following silicate feedstock amendment, but field-scale evidence remains limited. We report findings from a four-year ERW-reforestation experiment in South Wales, UK (11.5 ha; N = 64 plots), designed to capture ecosystem-level responses. The experiment used a fully factorial design that manipulated forest type (native broadleaf versus coniferous), feedstock amendment (amended versus unamended), and incorporated measurements of feedstock dissolution, pore water chemistry, soil CO₂ efflux, soil carbon pools, and aboveground tree biomass. Inorganic CDR was detectable but small: alkalinity export from upper soil layers corresponded to -0.19 ± 0.21 t CO₂eq ha^-1 yr^-1, with most weathering products remaining in the soil column. Organic pathways dominated cumulative system responses. Tree growth accelerated following metabasalt amendment, yielding an estimated -0.34 ± 0.07 t CO₂eq ha^-1 yr^-1 of additional aboveground CDR. By contrast, soil CO₂ efflux increased by 2.54 ± 4.04 t CO₂eq ha^-1 yr^-1, but with substantial variability across time and space. When integrated, these fluxes produced a net ecosystem carbon emission of 2.01 ± 4.05 t CO₂eq ha^-1 yr^-1 over the study period. Although belowground plant biomass was not directly quantified, plausible upper‑bound estimates (≈0.3–0.4 t CO₂eq ha⁻¹ yr⁻¹) do not alter the magnitude or direction of this net flux. Overall, ERW influenced CDR primarily through organic pathways, underscoring the need to better constrain plant-soil feedbacks before large-scale deployment. 

How to cite: Jones, G., Lancastle, L., Clayton, K., Epihov, D. Z., Zhang, Z., Averill, C., Smith, P., Beerling, D. J., Allen, H., Nicholls, C., Paschalis, A., and Waring, B.: Ecosystem responses determine the effectiveness of enhanced rock weathering for climate mitigation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5623, https://doi.org/10.5194/egusphere-egu26-5623, 2026.

Despite growing interest in enhanced weathering (EW)—the application of silicate rock powders to croplands—substantial uncertainty remains regarding its actual CO₂ removal potential. From a data perspective, small-scale laboratory experiments often indicate limited carbon uptake, but their representativeness of field conditions remains unclear. By contrast, field experiments yield highly variable results, but they face the challenge of quantifying percolation fluxes in open, heterogeneous, dynamic systems.

Here, we present a novel hybrid approach: a large-scale yet controlled laboratory experiment designed to quantify all soil percolation fluxes and EW-driven CO₂ removal. The experiment is conducted in an approximately 200 m² garden at the Politecnico di Torino (Italy), subdivided into three hydraulically isolated plots with different basalt applications: a control plot (no basalt), 3 kg m⁻², and 6 kg m⁻². Beneath the 50 cm soil profile, all percolating fluxes are collected, enabling direct measurement of drainage outflows and dissolved-ion fluxes. Combined with soil measurements, this setup can constrain the mass balance of the weathering products and their associated CO₂ removal potential.

Preliminary results from the first year of experiment show a small but statistically significant increase (≈ 50 µS/cm) in the electrical conductivity of percolating water in both high and intermediate application plots. This is accompanied by moderate increases in major cation and dissolved inorganic carbon concentrations. Changes in hydrological response and percolating dissolved nitrogen are also observed. Overall, this study aims to provide process-based evidence of EW performance at the plot scale, thereby improving the assessment and modelling of soil-based carbon dioxide removal strategies.

How to cite: Cannizzaro, F., Bertagni, M. B., Cagninei, A., Bosio, R., Fiorucci, A., and Boano, F.: A large-scale enhanced weathering experiment to quantify soil percolation fluxes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13246, https://doi.org/10.5194/egusphere-egu26-13246, 2026.

Large-scale carbon dioxide removal (CO₂) could be achieved through enhanced weathering (EW) deployment onto agricultural land and forests. Whilst the effects of EW treatment on soil and plant properties have been studied, impacts on soil gas fluxes remain poorly characterised. Soils both emit and uptake a wide range of gases, including greenhouse gases, such as nitrous oxide (N₂O), methane (CH₄) and CO₂, as well as reactive trace gases, such as nitric oxides (NO and NO₂), ammonia (NH₃), hydrogen (H₂) and volatile organic compounds (VOCs) which together influence climate and air quality either directly or indirectly through atmospheric reactions. EW can modify soil properties such as pH, organic carbon and structure, which can affect soil gas fluxes both directly, through physical and chemical processes, and indirectly via impacts on the soil microbiome. Therefore, characterising these responses is critical for determining potential co-benefits and trade-offs associated with large-scale EW deployment and informing monitoring, reporting and verification (MRV) frameworks.

In this laboratory study, fluxes of an extensive range of gases were measured from EW-treated soils collected from existing field trials across the UK on different land uses. Treated and control soils were sampled from arable land, grassland and newly planted mixed-broadleaf and monoculture-Sitka spruce forests. Soil fluxes of N₂O, NO, NO₂, NH₃, carbon monoxide (CO), ozone (O₃) and VOCs were measured online during controlled-temperature incubation experiments (5 to 25 °C with a step of 5 °C) using an advanced dynamic air-through chambers system equipped with high-resolution gas analysers and a proton-transfer-reaction mass spectrometer. CO₂ and CH₄ fluxes were measured online at room temperature using a separate gas analyser, whereas H₂ fluxes were measured offline from chamber headspace samples using gas chromatography.

Overall, we found no consistent pattern of EW effects across gases and land uses. Greenhouse gas fluxes had a land-use dependence, with arable soil showing increased N₂O uptake under EW treatment, CO₂ emissions decreasing in both forest soils, and CH₄ fluxes responding differently across sites, with increased emissions in arable soils but decreased emissions in grassland and increased uptake in broadleaf forest soils. Trace gases generally showed fewer and less systematic responses to EW, with no consistent patterns across land uses. These results suggest that land use and soil properties are important factors in determining soil gas responses to EW and highlight the need for land-use-specific monitoring strategies. Future in situ studies with in-depth soil characterisation will be essential to support robust MRV of EW and to assess potential co-benefits and risks of its large-scale implementation.

How to cite: Rees, K., Val Martin, M., Beerling, D., Bezanger, A., Cowan, N., Devlin, R., Hanlon, M., Langford, B., Medinets, S., and Drewer, J.: Effects of enhanced weathering on soil gas fluxes across UK land uses , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12483, https://doi.org/10.5194/egusphere-egu26-12483, 2026.

Rivers transport and transform products of chemical weathering, yet the processes governing carbonate precipitation, biotic transformation and fixation of enhanced rock weathering products remain poorly constrained. We conducted a controlled stream flume experiment manipulating simulated basalt-amended runoff across six ERW levels (0–100 t ha⁻¹) in groundwater- and river-fed systems to investigate calcite saturation state (Ω)  dynamics and ecosystem responses to alkalinity enhancement. Water chemistry and ecosystem responses were monitored for four weeks following alkalinity addition. Across all treatments and water types, flumes were generally calcite-supersaturated (Ω > 1), indicating baseline conditions favourable for carbonate precipitation. ERW treatments substantially increased supersaturation, and high temperatures combined with low flows led to Ω frequently exceeding 10 (a proposed precipitation threshold) and reaching > 50 under high-input scenarios. Relationships between Ca, CO₃²⁻ and Ω differed between groundwater- and river-fed systems, indicating that ERW effects on saturation state were mediated not only by cation supply but also by buffering capacity and carbonate speciation. Effects on benthic communities were weak, with invertebrate richness, abundance, and biomass being largely unaffected, though community composition contracted at the highest ERW level. Microbial respiration and primary production were generally only higher in groundwater-fed systems, while leaf litter and cellulose degradation were unchanged. Overall, these results indicate minimal ecological risk and demonstrate that thermokinetic conditions in small streams can support highly supersaturated calcite states during warm, low-flow periods without immediate carbonate precipitation. However, elevated supersaturation states may reduce carbonate solubility and increase the potential for secondary precipitation under changing hydrological or thermal conditions, representing a potential constraint on ERW-derived alkalinity transport efficiency within river networks.

How to cite: Macaulay, S., Khamis, K., Mignanelli, L., and Cavan, E.: Experimental insights into the role of running waters in Enhanced Rock Weathering, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21447, https://doi.org/10.5194/egusphere-egu26-21447, 2026.

Enhanced Weathering (EW) is increasingly discussed as a scalable carbon dioxide removal (CDR) approach, yet its real-world feasibility remains poorly constrained and is still largely inferred from modeling studies. Here we present results from an international systematic review and database effort that compiles reported CDR estimates alongside geochemical measurements and qualitative meta-data from the rapidly expanding EW literature, as well as from agronomic studies investigating silicate rock flour use as a fertilizer. Focusing on this agronomy-oriented rock flour literature, we leverage reported geochemical observations—including soil and porewater chemistry, changes in soil inorganic carbon stocks, cation exchange capacity and base saturation, and cation release from applied rock powders—to derive novel, observation-constrained estimates of EW-driven CDR. These geochemically derived estimates are integrated with reported CDR values from the broader literature to assess how deployment choices and quantification approaches influence inferred CDR rates. In addition, we systematically analyze reported agronomic responses to silicate rock flour applications, including crop yield and soil pH, to examine how agronomic performance co-varies with geochemical weathering signals and inferred CDR. Across both agronomic responses and CDR estimates, we find evidence for non-linear dose–response behavior with increasing rock application, indicating diminishing marginal benefits at higher rates in many contexts. This pattern suggests that a substantial fraction of agronomic utility and CDR may be achievable at relatively low application rates. The underlying database will be released open access to support transparent synthesis, scenario analysis, and measurement, reporting, and verification (MRV) development for EW research and applications.

How to cite: Suhrhoff, T. J. and the Enhanced Weathering Database and Meta-Analysis Team: Inferring Enhanced Weathering Carbon Dioxide Removal and agronomic impacts from agronomic studies using silicate rock flour: a systematic synthesis, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8280, https://doi.org/10.5194/egusphere-egu26-8280, 2026.

Terrestrial enhanced rock weathering (ERW) is a geoengineering technique that amends soils with crushed magnesium (Mg) and calcium (Ca) rich silicate rock to accelerate carbon dioxide removal (CDR) with the production of dissolved and solid carbonates. Although ERW is projected to store large amounts of inorganic carbon, up to 2 Pg carbon (C) per year (Beerling et al., 2020), significant uncertainty surrounds ERW research, with a critical question remaining as to how ERW affects soil organic carbon (SOC), the largest terrestrial C reservoir with 1550 Pg C globally. While increases to SOC after crushed rock additions could increase the carbon removal capacity of ERW, reductions in SOC could negate its benefits. Field-scale ERW studies examining SOC dynamics, remain few. Sokol et al. (2023), found that ERW can destabilize organic carbon, making a seemingly stable pool vulnerable to decomposition. Conversely, Xu et al. (2024) reported SOC increases four to eight times higher than soil inorganic carbon (SIC) growth in oxisols after CaSiO₃ amendments. These studies highlight that the effect of ERW on SOC is influenced by soil properties. I will address this gap in knowledge by gaining a comprehensive understanding of ERW’s impact on SIC and SOC pools across ten agriculturally relevant soils in the US with unique soil properties that have been previously taken from all major US ecosystems and climate zones (Davenport, 2024). My study involves a one year incubation assessment that leverages exploration of outcomes across a broad soil gradient under a controlled environment. My findings will elucidate what conditions (i.e., soil properties, climate) will lead to the greatest mitigation impact for targeting ERW deployments.

How to cite: Rivera, M., Viatkin, K., Oldfield, E., and Lehmann, J.: The impact of enhanced rock weathering on soil organic carbon, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15391, https://doi.org/10.5194/egusphere-egu26-15391, 2026.

Pyrogenic carbon capture and storage, enhanced weathering (EW), soil organic carbon (SOC) enhancement and biomass carbon capture are terrestrial carbon dioxide removal (CDR) methods that could be implemented on a short timescale. To maximize the CDR potential per area, these methods could be co-deployed and provide complementary co-benefits. This requires a substantial understanding of the ongoing reactions and interactions in the system at different scales, backed up by field data and dynamic models to estimate applicability and scalability of the method combination. Biochar and weathering of silicate rock powder have the potential to provide besides CDR also nutrients, change soil properties and affect plant growth, directly impacting soil organic carbon storage and biomass carbon capture. Nevertheless, the interactions between the amendments and their combined effects in the soil system are sparsely researched.

PyMiCCS as part of CDRterra addresses these knowledge gaps and  estimates the potential of the proposed combination of the different methods. The co-application of various biochars with rock powder as well as the co-pyrolysis of both amendments was realized and products characterized. The co-pyrolysis of biochar and rock powder can modify biochar properties, such as weight, porosity, nutrient content and stability. Furthermore, the application of materials to different soil types with and without crops was tested at various spatio-temporal scales. Biochar additions improved water circulation in clayey soils, while rock powders released nutrients. Furthermore, amendments increased SOC contents, with differences between combinations and single applications. While soil nutrient levels were elevated, no significant plant growth increases were observed in comparison to single applications. In the long-term, simulations for temperate climate and sandy soil suggest that the solo-biochar applications can increase non-biochar SOC by up to 300 kg ha^-1 yr^-1 per ton biochar and result in net ecosystem carbon uptake over 1000 years. Complementing experimental results and process-based modeling, an integrated economic assessment was conducted using a global land-use modelling framework. The analysis shows that the environmental and mitigation outcomes of biochar-based CDR depend on interactions between costs, agronomic yield responses, biochar persistence, application rates, and assumptions about carbon pricing or crediting. 

Overall, the results demonstrate that co-application of biochar and enhanced weathering can enhance soil carbon storage and nutrient dynamics, but side-specific assessments are needed, and amendments do not necessarily translate into increased crop yields. Our results highlight the substantial CDR potential and the importance of tailored evaluations, management strategies, and policy frameworks for their scalable and effective implementation.

How to cite: Linke, T., Amann, T., Ansari, M., Becker, J. N., Beer, C., Busch, F., Eschenbach, A., Hagemann, N., Hamburger, S., Kammann, C., Karstens, K., Maslouski, M., Meyer zu Drewer, J., Popp, A., Porada, P., Schmidt, H.-P., Vorrath, M.-E., Weindl, I., and Hartmann, J.: Potential of combining biochar and enhanced weathering and impacts on soil organic carbon and biomass: PyMiCCS project results, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19725, https://doi.org/10.5194/egusphere-egu26-19725, 2026.

Terrestrial enhanced weathering (EW) involves the application of crushed silicate-rich rock on soil which can then sequester inorganic CO₂ by forming bicarbonates and carbonates. However, more recently, the effects of EW on soil organic matter (SOM) cycling have been gaining increasingly more attention. An increase in soil pH and the release of nutrients from silicate minerals might activate microbes to decompose more SOM, thereby possibly offsetting CO₂ removed via the inorganic pathway. On the other hand, EW might promote SOM stabilization mechanisms that could increase the lifetime of carbon bound in SOM and strongly boost CO₂ removal by EW. There are two major pathways of SOM stabilization in soils. Firstly, EW can increase formation of mineral-associated organic matter (MAOM) by forming highly reactive secondary minerals such as (hydr)oxides and other clay-sized minerals that can chemically bind SOM. Secondly, the formation of stable aggregates can physically protect SOM from microbial decomposition. While these stabilization mechanisms could greatly elevate the potential of EW, they have received little attention compared to the inorganic CO₂ removal pathway of EW. Studies that focused on SOM stabilization mechanisms by EW have been showing contrasting, possibly context-depending effects. Therefore, more experimental data is needed to unravel the complex network of interactions between EW and SOM stabilization.

Co-deployment of EW with biochar (biomass stabilized via pyrolysis) could promote the CO₂ removal efficiency even further. To date, studies that combined EW with biochar application remain scarce, limiting our understanding on how the two technologies interact. Biochar application can stimulate, slow down or exhibit neutral effects on SOM decomposition. Given the potential for co-deployment of EW and biochar in agricultural soils, there is a need for understanding interactions between EW, biochar and SOM.

In a mesocosm experiment we mixed basalt and poplar wood biochar with a sandy loam soil in a full factorial design. We quantified SOM stabilized in aggregates and via mineral association after 9 and 21 months. Aggregates were separated by size via wet sieving and their carbon content was quantified via loss on ignition (4h at 550 °C). Subsequently, the smallest size fraction (<50 µm) was used to target different organo-mineral associations via sequential extractions to determine MAOM formation. Results will be shown at the conference.

How to cite: Roussard, J., Cosgrove, M., Vandecasteele, B., and Vicca, S.: Does co-deployment of enhanced weathering and biochar affect soil organic matter stabilization?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18456, https://doi.org/10.5194/egusphere-egu26-18456, 2026.

Enhanced rock weathering (ERW) is an emerging carbon dioxide removal (CDR) strategy that can support net-zero emission targets. However, current ERW modelling efforts rely on assumptions that introduce substantial variation in CDR estimates across varying ecosystems and hydroclimatic conditions. They typically ignore or oversimplify plant–soil interactions and high-frequency hydrological dynamics, obscuring short-term weathering responses and biotic feedbacks to soil moisture dynamics. Here, we introduce an integrated, process-based modelling framework, T&C-SMEW, which represents ecohydrological and ERW dynamics, along with microbially explicit biogeochemical processes. We compared framework simulations against a controlled mesocosm experiment and long-term field observations, demonstrating its ability to reproduce feedstock cation release, soil pH dynamics, gross primary production, and CO2 fluxes. T&C-SMEW reveals hydrological constraints and vegetation effects on ERW-mediated CDR by quantifying impacts on ecosystem respiration, net ecosystem exchange, and alkalinity export, emphasising the importance of ecohydrological modelling for ecosystem-level CDR estimation. These advances provide a modelling framework for identifying optimal deployment scenarios to establish ERW as a viable and operationally feasible CDR approach.

How to cite: Zhang, Z., Jones, G., Calabrese, S., Bertagni, M., Fatichi, S., Waring, B., and Paschalis, A.: An Integrated Modelling Framework to Determine Terrestrial Carbon Dioxide Removal via Enhanced Rock Weathering, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11419, https://doi.org/10.5194/egusphere-egu26-11419, 2026.

Although enhanced weathering is a promising CDR technology, experimental evidence from the past years have tempered expectations and call for caution. These experiments show two major things: first the impact on soil organic matter (SOM) can be large and, particularly in the short term, can lead to enhanced carbon dioxide emissions rather than the hoped for carbon dioxide removal. Second, very limited (or no) leaching of alkalinity to deeper ground water is observed, and instead the cations released from weathering end up locally in different soil pools.

Advancing our understanding of this inorganic-organic (IC-OC) coupling requires the development of numerical models that couple inorganic and organic carbon cycles. Here we present the implementation of several established SOM models in the geochemical software platform PhreeqC. This well established platform has a strong track record in simulating soil water chemistry and allows for a flexible selection of a broad range of geochemical processes. We show how different models and different ways of coupling affect simulated behavior of CO2 exchange with the atmosphere and alkalinity fluxes towards ground-water, how they compare to observed data from selected experiments and elaborate on the challenges involved.

How to cite: Cox, T., Vandenhove, C., Vienne, A., Janssens, I., and Vicc, S.: Inorganic-Organic Carbon coupling in models for enhanced weathering., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22127, https://doi.org/10.5194/egusphere-egu26-22127, 2026.

Quantifying carbon dynamics during enhanced weathering has been challenging, given spatial and temporal soil heterogeneity, complex biogeochemical interactions, and limitations in measurement resolution. For example, intensive and repeated sampling campaigns over the duration of several years are required to detect changes in soil organic carbon (SOC) stocks given that a comparatively small shift needs to be detected in a large pool with high spatial heterogeneity. Thus, low signal-to-noise ratios often prevent the detection of shifts, as EW induced changes in SOC stocks are often below the natural variability of SOC. Given the high uncertainty associated with both, SOC sequestration estimates but also CO₂ removal estimates, the integration of Bayesian approaches into modelling efforts could be particularly valuable. Bayesian modelling frameworks offer a powerful tool, explicitly integrating experimental observations with mechanistic understanding and prior knowledge, while quantifying uncertainty across all model components, thereby also accounting for soil heterogeneity.

In our presentation we will illustrate the advantages of Bayesian analyses via a model developed for soil CO₂ efflux partitioning (in rhizosphere respiration and SOM decomposition). Soil CO₂ flux partitioning is an important tool to inform EW effects on organic C dynamics that requires a sequence of calculations and the combination of different data sources. Several sources of uncertainty arise which often remain unaccounted for in conventional partitioning approaches (e.g. the regression used during the determination of the isotopic signature of the soil CO₂ efflux extrapolates far beyond measured data, isotopic fractionation due to physical and/or biological processes, CO₂ originating from soil carbonates, CO₂ removal due to enhanced weathering, etc.). A Bayesian model allows the integration of such diverse datasets with different structures flexibly while explicitly accounting for variability in the data and for sources of uncertainty. Given its probabilistic framework, outputs are expressed as probability distribution rather than point estimates, therefore yielding far more informative results.

Further developing this model, potential applications could include the joint assessment of organic C sequestration and inorganic CO₂ removal. Thus, building on this example, we will discuss how Bayesian approaches could be further developed to support monitoring, reporting and verification (MRV) efforts for enhanced weathering.

How to cite: Steinwidder, L., Ogle, K., Boito, L., and Vicca, S.: Accounting for uncertainty in carbon fluxes: Towards the integration of Bayesian approaches in enhanced weathering, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18487, https://doi.org/10.5194/egusphere-egu26-18487, 2026.

Carbon dioxide removal (CDR) is an essential and integral part of the European Climate Law, while the Intergovernmental Panel on Climate Change (IPCC) recognizes CDR as a “necessary element” to keep global warming well below 2°C, let alone 1.5°C. There is extensive debate in expert and policy circles about the role of CDR for achieving ambitious climate objectives. Engaging with publics around CDR technologies is crucial, however, given their broad unfamiliarity and the potential for backlash once technologies are deployed more widely (if not earlier).

Though there is an increasingly rich literature on public perceptions of CDR, several key gaps remain. First, there is a tendency to neglect those in the global South. Second, though there has been an understandable focus on climate beliefs and beliefs about science and technology, there is little consideration of the individual differences to take risks, delay outcomes, and act pro-socially (i.e. “economic preferences”). The broad importance of economic preferences has been established across various domains. As CDR becomes a more commercially viable (and less hypothetical) proposition, such economic preferences are also more likely to have meaning.

Using cross-country, nationally representative surveys in five countries (China, Germany, US, Brazil, Kenya; 4000 participants), we examine perceptions and support of CDR technologies and climate policies. Following our pre-registered hypotheses, we employ regression analysis to establish whether six types of economic preferences (risk-taking, patience, altruism, positive reciprocity, negative reciprocity, trust) predict support for three CDR technologies: direct air capture; afforestation and reforestation; enhanced rock weathering. We employ validated measures from Falk et al. (2018) as the key determinants, along with variables for climate beliefs, environmental identity, science and technology beliefs; and trust in responsible institutions. These additional variables will be examined as potential moderating factors of the relationship between economic preferences and CDR support.

How to cite: Baum, C. M., Lades, L., Fritz, L., and Sovacool, B.: Do economic preferences predict public support for different carbon dioxide removal technologies?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2563, https://doi.org/10.5194/egusphere-egu26-2563, 2026.